1. Field of the Invention
The present invention relates to a diopter adjusting mechanism for a single lens reflex camera incorporating a photosensitive measurement of the light intensity of the object scene through the objective lens of the camera, and more particularly it relates to an improved viewfinder having an eyepiece shutter and diopter adjusting mechanism that is particularly compact.
2. Description of the Prior Art
A number of different viewfinders have been proposed for single lens reflex cameras that incorporate a shutter blind or shield such as U.S. Pat. Nos. 3,613,543 and 3,902,183. The purpose of these shields in a single lens reflex camera of the through the lens (TTL) light measurement type is to prevent external light from coming in through the eyepiece aperture which would produce errors in the resulting light measurement of the object scene. These errors can be excessive, particularly when the outside of the eyepiece is not covered by the face of the photographer, such as occurs in self timer photography.
An additional problem exists in the fact that photographers have limited and variable focusing powers of their own eyes. Thus it is often difficult for near sighted, far sighted or presbyopic persons to observe an image formed in front of the eye through the camera. There have been various suggestions in the prior art to provide diopter adjustment to the camera eyepiece, for example by moving the eyepiece along the optical axis. Movement of the eyepiece however, not only effects the viewfinder magnification but requires substantial space that is at variance with the design objectives of the compact cameras of today. Additionally, the incorporation of an eyepiece shutter can add additional space requirements in the design of the camera.
In view of the compact design objectives required in modern cameras along with the necessity of providing numerous ancillary features, such as the eyepiece shutter and diopter adjustment, there still remains a demand in the prior art to solve these specific problems.